Electron beam source and method of manufacturing the same

ABSTRACT

A tip of an electron beam source includes a core carrying a coating. The coating is formed from a material having a greater electrical conductivity than a material forming the surface of the core.

CROSS-REFERENCE TO RELATED APPLICATION

This application claims priority under 35 U.S.C. §119 to German PatentApplication 10 2008 049 654.5 filed Sep. 30, 2008. The contents of thisapplication is hereby incorporated by reference in its entirety.

FIELD

The disclosure relates to an electron beam source and to a method ofmanufacturing and using an electron beam source. The electron beamsource can be capable of providing an electron beam having a highbrightness and/or a small energy spread.

BACKGROUND

Conventional electron beam sources include an electrode from which anelectron beam may be extracted by exposing the electrode to anelectrical potential, a thermal excitation, a photonic excitation or acombination of an electrical potential, thermal excitation and photonicexcitation.

SUMMARY

In some embodiments, the disclosure provides an electron beam sourceincluding an electrode tip having a comparatively small radius.

In certain embodiments, the disclosure provides an electron beam sourcewhich can be easily manufactured or handled.

In some embodiments, the disclosure provides an electron beam sourcewhich has high durability.

In some embodiments, an electron beam source is provided having a tipwhich includes a core. The core is at least partially provided with aconductive coating.

In certain embodiments, the surface of the core is formed of a materialhaving a lower electrical conductance than the material of the coating.Since the tip of the electron beam source may be very small, it may bedifficult to measure the conductivities of the materials from which thetip is formed at the tip itself. In the context of the presentdisclosure, values of conductivities or values of a modulus ofelasticity of materials which are employed for forming the tip thereforerelate to values of resistance and modulus of elasticity, respectively,which may be measured in the bulk of the respective material.

In some embodiments, a further material having a comparatively lowerelectrical conductivity is provided below the coating of thecomparatively conductive material which at least partially provides thesurface of the tip. It is possible that the coating of the materialhaving the greater conductivity is directly applied onto a surfaceformed by the further material having the comparatively lowerconductivity and that both materials directly contact each other.However, it is also possible that a layer from still a further materialis arranged between the two above-noted materials, for example toimprove an adherence of the coating made from the material having thegreater conductivity at the material having the lower conductivity.

In certain embodiments, the core whose surface is provided by thematerial having the lower conductivity and on which the coating made ofthe material having the higher conductivity is applied consists of aninner core and a layer of the material having the lower conductivityapplied thereon. Thereby, the inner core is formed from a third materialwhich may be different from the material having the lower conductivityand which in particular may have a higher electrical conductivity thanthe material having the lower conductivity.

In some embodiments, the third material of which the inner core is madehas a modulus of elasticity of greater than 150 kN/mm² (e.g., greaterthan 300 kN/mm², greater than 600 kN/mm², greater than 700 kN/mm²).

The elastic modulus of an object is defined as the slope of itsstress-strain curve in the elastic deformation region, i.e. the ratiobetween the force causing a deformation divided by an area to which theforce is applied and the ratio of a change caused by the stress to anoriginal state of the object. The elastic modulus of a material may bemeasured by applying a pressure along an axis and determining a relativedeformation of the material along that axis.

In particular the modulus of elasticity of the third material may begreater than that of plastic material. In particular the hardness of thethird material is greater than that of plastic material. Thus, the tipis rigid to withstand forces acting on the tip when an electric field isgenerated. Therefore the shape of the tip and the shape of the entireelectron source is maintained and thus the distribution of the electricfield generated is substantially maintained to favourably emitelectrons.

In certain embodiments, the third material of which the inner core ismade has a modulus of elasticity of less than 1100 kN/mm² (e.g., lessthan 1000 kN/mm², less than 800 kN/mm²). The third material may bediamond like carbon which has a modulus of elasticity of about 770kN/mm².

In some embodiments, a center of the core is formed of the firstmaterial which may have a modulus of elasticity of greater than 150kN/mm² (e.g., greater than 300 kN/mm², greater than 600 kN/mm², greaterthan 700 kN/mm²). The first material may have a modulus of elasticity ofless than 1100 kN/mm² (e.g., less than 1000 kN/mm², less than 800kN/mm²).

In certain embodiments, the layer from the first material on the innercore has a thickness of more than a monolayer from the layer material.Exemplary thicknesses are in ranges from 0.1 nm to 100 nm, such as from1 nm to 50 nm, or from 1 nm to 30 nm.

The coating from the material having the greater conductivity applied tothe core may have a thickness of 2 nm to 50 nm (e.g., from 2 nm to 30nm, from 20 nm to 50 nm). In some embodiments, the tip is fixed at thebase and its end extending away from the base has a surface having asmall radius of curvature. In some embodiments, the radius of curvatureis less than 100 nm (e.g. less than 80 nm, less than 60 nm). In certainembodiments, the radius of curvature is greater than 5 nm, such asgreater than 10 nm.

In some embodiments, a maximum dimension of the tip in its longitudinaldirection may be greater than 50 nm (e.g., greater than 100 nm, orgreater than 300 nm). In certain embodiments, a maximum dimension of thetip in its transversal direction may be less than 500 nm (e.g., lessthan 200 nm, less than 100 nm, or less than 50 nm).

In certain embodiments, a ratio between the extension of the tip in thelongitudinal direction and the dimension of the tip in the transversaldirection (aspect ratio) may be greater than 2:1 (e.g., greater than5:1, greater than 10:1, or still greater). Further, the tip may tapertowards its end.

In some embodiments, an electrical conductivity of a material at leastpartially providing the surface of the tip may be greater than 10⁻⁷ S/m(e.g., greater than 10⁻⁵ S/m, greater than 10⁻³ S/m, greater than 10⁻¹S/m, greater than 10² S/m, greater than 10⁴ S/m, or greater than 10⁶S/m).

In certain embodiments, a material providing a surface of a core of thetip onto which core a coating from a material having a comparativelygreater electrical conductivity is applied may have an electricalconductivity which is less than 10⁵ S/m (e.g., less than 10³ S/m, lessthan 10 S/m, less than 10⁻¹ S/m, less than 10⁻³ S/m, less than 10⁻⁵ S/mor less than 10⁻⁷ S/m).

In some embodiments, a ratio between an electrical conductivity of acoating material applied onto a core of a tip of an electron beam sourceand an electrical conductivity of a material onto which the coating isapplied may be greater than 10:1 (e.g., greater than 100:1, greater than10⁴:1, greater than 10⁶:1, or greater than 10⁸:1).

In certain embodiments, a material onto which a coating of a tip of anelectron beam source is applied is formed from diamond like carbonmaterial. Diamond like carbon material is amorphous carbon materialhaving some of the properties of natural diamond. In particular, diamondlike carbon includes substantial amounts of sp³-hybridized carbon atoms.Today seven forms of diamond like carbon are known. Of these sevenforms, there are three hydrogen free forms which are denoted as a-C,pa-C, and a-C:Me, where the latter includes a metal (Me) as dopant. Ofthe seven forms, there are four hydrogenated, hydrogen including forms,which are denoted as a-C:H, ta-C:H, a-C:H:Me, and a-C:H:X, wherein thetwo latter include a metal (Me) and other elements (X), respectively, asdopant. The metals Me may include tungsten, titanium, gold, molybdenum,iron and chromium, among others, and the other elements X may includesilicon, oxygen, nitrogen, fluorine, and boron among others.

There are different methods known for manufacturing diamond like carbon.These methods have in common, that the material is deposited onto asubstrate, where pressure, energy, catalysis, or a combination of thesame is used to deposit atoms so that these atoms form a sp³-bond withalready deposited carbon atoms to a significant percentage.

In some embodiments, a diamond like carbon material may be doped withdifferent elements, such as Au, Mo, Fe, Cr and others.

In certain embodiments, a material which is applied as a coating onto acore of a tip of an electron source and which forms at least a portionof its surface is a metal. The metal also may have an oxide layer thatdecreases the work of emission for electrons in some situations.Examples of metals include Ti, Pt, Al, W, WTi, V, Hf, Zr and others aswell as oxides of these, such as TiO_(x), VO_(x), HfO_(x), ZrO_(x) andothers.

In some embodiments, the material which is applied as a coating onto acore of a tip is a semiconductor material. Examples of semiconductormaterials include Ge and/or GaAs.

In certain embodiments, an electron beam source includes a tip fixed ata base and extending away from the base. The tip includes a core havinga surface formed of a first material. The tip also includes a coatingformed of a second material. The second material is applied to the core.The second material at least partially forms a surface of the tip. Afirst electrical terminal is electrically connected to the coating. Anextraction electrode has an opening arranged opposite to the tip. Asecond electrical terminal is electrically connected with the extractionelectrode.

In some embodiments, a surface of the base includes a convex surfaceportion extending around an end of the tip close to the base. The convexsurface contributes to favourably shaping an electric field for emittingelectrons from the tip.

In certain embodiments, a radius of curvature associated with the convexsurface portion of the base is between 10 μm and 0.1 μm (e.g., between 3μm and 0.3 μm, between 0.6 μm and 0.4 μm).

In some embodiments, the base has a surface portion having a surfaceshape of axial symmetry relative to an axis of symmetry. An anglebetween the axis of symmetry and a longitudinal direction of the tip isless than 10°. This further ensures that the electric field around thetip which generated when suitable electric potentials are applied to thebase and to the extraction electrode is favourably shaped for emittingelectrons from the electron source.

In certain embodiments, a tip including a coating on a core may beemployed as tip of an electron beam source. The electron beam source isintegrated in an electron beam system that includes among the source oneor more beam shaping components, such as an aperture, an electronoptical lens, a beam deflector or the like. The tip may be used togenerate an image of an object using electrons. For example, the tip maybe used to generate of one or more primary beams of an electronmicroscopic system.

In some embodiments, the tip may be used to generate one or more writingbeams to expose a beam sensitive layer with a predetermined pattern. Forexample, the tip may be used in an electron lithography system.

In certain embodiments, a method for manufacturing an electron beamsource is provided. The method includes growing a core from a firstmaterial onto a base using deposition, and applying a coating from asecond material onto the core. In some embodiments, the deposition mayinclude electron beam induced deposition, ion beam induced deposition,growing the base from amorphous carbon, from a local catalyst, which wasfor example applied using a lithography method or ion deposition, andother methods.

BRIEF DESCRIPTION OF THE DRAWINGS

Embodiments of the disclosure are subsequently explained in more detailreferring to drawings, in which:

FIG. 1 is a schematic illustration of an electron beam system;

FIG. 2A is a schematic sectional illustration of an electron beam sourceused in the electron beam system of FIG. 1;

FIG. 2B schematically illustrates geometric properties of the electronbeam source shown in FIG. 2A and employed in the electron beam system ofFIG. 1;

FIG. 3 is a photograph of a tip of the electron beam sourceschematically illustrated in FIG. 2A;

FIG. 4 is a schematic sectional illustration of an electron beam source;and

FIG. 5 is a flow diagram for a method of manufacturing an electron beamsource.

DETAILED DESCRIPTION

Exemplary embodiments of the disclosure are explained below in thecontext with the Figures. Thereby, components corresponding to eachother with respect to their structure and function are denoted by thesame numeral but are denoted for distinction with an additional letter.For explaining the components it is therefore also referred to theentire respective preceding or succeeding description.

FIG. 1 is a schematic illustration of an electron beam system. Theelectron beam system 3 includes an electron beam source 5 having acathode 7 which is described in more detail below, and having twosuccessively arranged anode apertures 6 and 8 each providing an opening9. The two electrodes 6 and 8 are arranged close to the cathode suchthat the openings 9 are arranged opposite to a tip of the cathode andsuch that the openings 9 are traversed by an electron beam 13, when thesource 5 is operated. The electron beam 13 generated by the source 5traverses a condensor lens 11 and an opening 15 in a secondary electrondetector 17 and is directed onto a location 21 at a surface 23 of anobject 25 by further electron optics 19. In the schematic illustrationof FIG. 1 electron optics 19 include a magnetic objective lens 27 andmay further include magnetic or electrostatic lenses and electrodeswhich are not illustrated in FIG. 1. Optics 19 further includedeflectors 29 to deflect the electron beam 13 from its straightpropagation so that the electron beam may be directed to selectablelocations 21 within an extended region 31 at the surface 23 of theobject 25.

The electrons of the electron beam 13 release secondary electrons at thelocation 21 at which they impinge onto the object. The secondaryelectrons are accelerated away from the surface 23 of the object 25 byan electrode 22 at which an appropriate voltage is applied and thesecondary electrons enter into the objective lens 27. Exemplarytrajectories of such secondary electrons are denoted by reference sign37 in FIG. 1. A portion of the secondary electrons impinges at thedetector 17 and is detected there.

A controller 33 is configured to supply, via lines 35, 36, a currentthrough the cathode 7 of the electron source 5, to heat the same ifdesired. In general the cathode may be operated without heating. Thelines 35, 36 further serve to apply a predetermined electricalpotential, for example referred to ground potential, at the tip of thecathode 7. Lines 37 and 38 serve to apply a respective predeterminedelectrical potential with respect to the tip of the cathode 7 to the twoelectrodes 6 and 8, so that an emission of electrons from the tip isassisted and so that a distribution of the electrical field in theregion of the tip favourably causes forming the beam 13 from theelectrons emitted from the tip. Via a line 39 a predetermined electricalpotential with respect to the anode 7 is applied by the controller 33 toa holder 24 for the object 23 and thus to the object 23 itself so thatthe electrons of the beam 13 impinge at the object 25 with apredetermined kinetic energy. The secondary electrons thereby releasedand impinging onto the detector 17 generate signals in the detectorwhich are read out from the controller 33 via line 41. Via control line42 the controller 33 controls the deflector 29 to shift the location 21at which the electron beam 13 impinges onto the object 25. By recordingthe signals supplied by the detector 17 depending on the deflection ofthe electron beam 13 it is possible to gain electron microscopic imageinformation from the object 25.

As far as described above the electron beam system 3 has the function ofan electron microscope of type SEM (scanning electron microscope).However, some embodiments also include other types of electron beamsystems, such as for example electron microscopy systems of type LEEM(low electron emission microscope) and of type TEM (transmissionelectron microscope). Certain embodiments include lithography systems inwhich one or more electron beams are employed to expose a beam sensitivelayer (resist) with a predetermined pattern. Hereby, an electron beammay again systematically be scanned in the way described in the contextof FIG. 1 across the beam sensitive layer and may thereby be controlledin its intensity, to expose selective regions of the beam sensitivelayer with the energy of the impinging electrons. The intensity of thebeam impinging onto the layer may thereby be varied by controlling thesource or a separate beam blanker may be provided to switch the beam onand off. The beam sensitive layer exposed in this way may subsequentlybe developed and may be subjected to further lithographical steps, suchas for example ion implantation, sputtering or material deposition, tomanufacture miniaturized components.

FIG. 2A is an illustration of a detail of the electron beam source 5 ina cross section. The electron beam source 5 of the embodiment shown hereincludes a carrier plate 51 which may for example be formed from metalthrough which also a current may flow to heat the cathode. The carrierplate 51 has a terminal for a control line to apply a predeterminedelectrical potential relative to other components in an electron beamsystem to the cathode.

A base 53 is fixed at the plate 51 in which base a cylindrical recess 55is provided. A material for the base 53 may for example be silicon, andthe recess 55 may for example be realized by etching into the body ofthe base 53. A core 57 of a tip 60 of the cathode 7 is fixed in therecess 55. The core may be formed from an electrically substantiallynon-conductive material. For example its electrical conductivity may beless than 10⁻⁶ S/m. In the embodiment illustrated here the core is madefrom diamond like carbon. One possibility to manufacture the core 57made of diamond like carbon is the application of an electron beaminduced deposition. In this method the base is placed into a vacuumchamber in which a predefined atmosphere of process gas prevails forwhich for example carbon compounds may be employed. In this methodfurther an electron beam is directed to the bottom of the recess 55 tostart the deposition of diamond like carbon at this location. Byselectively directing the electron beam onto those locations at which ata given moment during the process carbon material should be depositedthe process gas is exited to deposit carbon atoms at the surface suchthat these at least partially form an sp³-bond with carbon atoms alreadydeposited at this location. Hereby it is also possible, to choose theprocess gas such that the depositing material contains (besides carbon)dopants, such as for example hydrogen.

In the example described here the deposition was controlled such thatthe core 57 has a dimension 1 in a direction extending away from thebase 53 of about 560 nm. Further, the deposition was designed such thatthe core has a substantially round cross section, namely with a maximaldimension b orthogonal to the longitudinal direction of about 150 nmclose to the base, wherein the cross section of the core 57 continuouslytapers towards its end distant from the base 53. At the end distant fromthe base 53 the core has a radius of curvature r1 at the surface ofabout 13 nm.

Using the described method the tip may be grown on the base with a highangular velocity. A longitudinal axis of the tip may for example beoriented such that it includes an angle of less than 0.5° with asymmetry axis of the base and may be spaced apart from the symmetry axisof the base less than 0.1 mm.

A surface of the core 57 is coated with a conductive coating 59 from Tiand TiO_(x). This coating has a coating thickness c of 10 nm and was forexample applied onto the core 57 by sputter coating or electron beamevaporation. This coating also extends across the surface of the base 53up to the plate 51 so that a comparatively good electric connection isestablished between the plate 51 and the end of the tip 7 distant fromthe base 53. In the state schematically illustrated in FIG. 2A also theend of the core 57 pointing away from the base 53 is covered with thecoating 59 so that an outer surface of the cathode 7 has a radius r2 ofcurvature of about 23 nm at this end.

FIG. 2B illustrates further geometrical properties of the electron beamsource 5 of FIG. 2A. The base 53 has an exposes a surface 53′, whereinthe exposed surface 53′ is provided by the conductive coating 59. Othersurface regions of the base 53 may be exposed during manufacturing theelectron source, such as for example the recess 55 at which the tip 60is fixed. However, the recess 55 is not exposed in the completedelectron source. A region 52 defines a portion of the exposed surface53′ of the base 53. This surface portion may amount to at least 50%,such as at least 80%, of an entire exposed surface 53′ of the base. Thethus defined surface portion extends around an end of the tip 60 closeto the base 53. This surface portion has a convex shape. However, notthe entire exposed surface 53′ of the base need to be convex.

The shape of the convex surface portion of the surface 53′ of the base53 may be approximated by a spherical surface by fitting a sphere havinga center C and having an appropriate radius R at the convex surfaceportion, as illustrated in FIG. 2B. In the illustrated example the bestfitting sphere has a radius R=0.5 μm which corresponds to a radius ofcurvature of the surface portion of the exposed surface 53′. In otherembodiments the radius of curvature R may be between 0.1 μm and 10 μm.

In the illustrated example the shape of the surface portion of the base53 around the tip 60 is axially symmetric having a symmetry axis 54. Thesymmetry axis coincides with a longitudinal axis 61 of the tip 60. Inother embodiments the base may be rotationally symmetric having asymmetry axis. In other embodiments the longitudinal axis 61 of the tip60 and the symmetry axis 54 of the base 53 include an angle of less than10°.

FIG. 3 shows a photograph of the cathode 7 described above withreference to FIGS. 2A and 2B.

A cathode of the constitution shown in FIG. 3 is capable of generatingan electron beam of comparatively large intensity over a relatively longtime. In a performed experiment a beam current of 3 μA was achieved andcould be maintained over a time span of 1500 hours. Thereby, the beamcurrent stayed comparatively constant, wherein maximum currentoscillations of 10% occurred, while current oscillation were less than3% over a time span of some minutes.

An explanation of the capability of the construction shown in FIG. 2 aselectron beam source is still not entirely possible by the inventors.According to speculations an explanation may be seen in that themanufactured construction has a relatively large ratio between lengthand width and a small radius at the tip so that a favourableamplification of the electrical field results there. Another reason maybe that the material of the core has a large durability and resistsbombardment by ions of a residual gas in the vacuum chamber presentaround the tip during a long time, wherein the bombardment occurs duringthe operations. Even if the coating 59 at the end of the tip is degradeddue to such a bombardment a good emission of electrons may neverthelessoccur, since the tip conducts the electrons across the coating 59extending cylindrically around the core 57 up to the end of the tip.According to further considerations the electrons emitting from the tipmove within the conductive coating having the form of a face of acircular ring in which states of the electrons are quantized. The energylevels for electrons in the coating resulting thereby are occupied suchthat the work of emission from the coating is relatively low forelectrons residing in one of the higher occupied energy levels or suchthat a tunneling probability for electrons out of the tip is relativelyhigh.

FIG. 4 shows a further embodiment of a tip 60 a for an electron beamsource 7 a. The tip 60 a shown in FIG. 4 has a similar construction anda similar function as the tip explained referring to FIGS. 2A and 2B. Incontrast thereto, however, the core 57 a is however not integrallyformed from a single material piece. Rather, the core 57 a has an innercore 65 having a longitudinally extending shape and having a roundedsurface at its end distant from a base 53 a. The inner core 65 is coatedwith a layer 57 a from a non-conductive material. The layer 57 a isfurther coated with a coating 59 a from conductive material so that thecoating 59 a extends up to the end of the core 57 a distant from thebase 53 a and further extends up to a plate 51 a at which the base 53 ais held to provide a conductive connection between the plate 51 a andthe end of the core 57 a distant from the base 53 a.

Similar to FIGS. 2A and 2B, the tip 60 a thus includes a conductivecoating 59 a at least partially providing its surface, wherein thecoating 59 a is applied in a region of the tip onto a non-conductivematerial 63. Therefore, it is possible that the inner core 65 is formedfrom a material which itself is conductive or non-conductive.

Exemplary materials for the inner core are diamond like carbon,exemplary materials for its layer 57 a are SiO₂ and exemplary materialsfor the outer coating 59 a are Ti and TiO_(x).

A method for manufacturing an electron beam source is explained belowreferring to FIG. 5. The method starts with a step 101 in which a baseis provided at which an appropriate tip is fixed in the subsequentsteps. Therefore, in a step 103, a core of the tip is grown on the base.In FIGS. 2A, 2B and 4, the base exhibits a recess in which the growingcore is fixed. However, it is also possible to grow the core directly ona smooth surface of the base, i.e. not in a recess of the same, suchthat the core is sufficiently fixed at the base. After growing the coreof the tip such that it exhibits a desired length, a desired crosssection and a desired tapering towards its end distant from the base, ifdesired, the core is coated with a conductive material in a step 105.With step 105 a method for manufacturing a tip for an electron beamsource according to an embodiment of the disclosure is completed.

The method for manufacturing the electron source according to theembodiment of the disclosure explained here includes a subsequentfurther step 107 in which the tip with the base is assembled to anelectron source. Thereby, one or more apertures are arranged relative tothe base such that the aperture is located opposite to the tip so that,upon applying an electrical voltage between the aperture and the base, adistribution of the electrical field between the aperture and the tipresults such that electrons can be extracted from the tip and formedinto a beam. With the assembly into the electron beam source in the step107 an embodiment of the method for manufacturing an electron beamsource is completed.

In contrast, manufacturing an electron beam system still includes afurther step 109 in which the electron beam source is installed intosuch an electron beam system. The electron beam system may for examplebe an electron microscopy system or an electron lithography system.

The core may be deposited onto the base by electron beam induceddeposition. However, it is also possible to employ other methods fordeposition onto the base, such as for example catalytically growingamorphous carbon. Further, it is possible to also manufacture the corewith a tip of a small tip radius in that an initially larger blank isreduced in its dimension by directed ablation. Examples of such methodsare milling processes using gallium ions or argon ions.

It is further possible to use a tip such as one employed for a scanningtunneling microscope or an atom force microscope as core for a tip of anelectron beam source according to an embodiment of the disclosure. Anexample is an AFM probe which may be purchased from the companynano-tools GmbH, 80469 Munich, Germany. Then the step 105 of coatingwith a conductive material is still to be applied to the thus obtainedcore to obtain a tip for an electron beam source according to anembodiment of the disclosure.

In some embodiments, a tip of an electron beam source includes a corecarrying a coating. The coating is formed from a material having agreater electrical conductivity than a material forming the surface ofthe core.

1. A source, comprising: a base; a tip fixed to the base and extendingfrom the base, the tip comprising: a core having a surface comprising afirst material; and a coating applied to the core, the coatingcomprising a second material, the second material forming a surface ofthe tip; a first electrical terminal electrically connected to thecoating; an extraction electrode having an opening; and a secondelectrical terminal electrically connected to the extraction electrode,wherein: the source is an electron beam source; and at least one of thefollowing conditions is fulfilled: an electrical conductivity of thefirst material is less than 10⁵ S/m; an electrical conductivity of thesecond material is greater than 10⁻⁷ S/m; and a ratio of the electricalconductivity of the second material to the electrical conductivity ofthe first material is greater than 10:1.
 2. The source according toclaim 1, wherein a surface of an end of the tip that is distal from thebase has a radius of curvature that is less than 100 nm.
 3. The sourceaccording to claim 1, wherein a dimension of the tip in its longitudinaldirection extending away from the base is at least 2 times greater thana maximum dimension of the tip in a direction that is orthogonal to thelongitudinal direction of the tip.
 4. The source according to claim 1,wherein a maximum dimension of the tip in its longitudinal direction isat least 50 nm.
 5. The source according to claim 1, wherein a dimensionof the tip in its transverse direction is at least 500 nm.
 6. The sourceaccording to claim 1, wherein a thickness of the coating of the secondmaterial is at least 2 nm.
 7. The source according to claim 1, wherein athickness of the coating of the second material is less than 50 nm. 8.The source according to claim 1, wherein a center of the core comprisesthe first material.
 9. The source according claim 8, wherein the firstmaterial has a modulus of elasticity that is greater than 150 kN/mm².10. The source according to claim 8, wherein the first material has amodulus of elasticity that is less than 1100 kN/mm².
 11. The sourceaccording to claim 1, wherein the core of the tip includes an inner corecomprising a third material different from the first material, and alayer comprising the first material is applied onto the inner core. 12.The source according claim 11, wherein the third material has a modulusof elasticity that is greater than 150 kN/mm².
 13. The source accordingto claim 11, wherein the third material has a modulus of elasticity thatis less than 1100 kN/mm².
 14. The source according to claim 1, whereinthe first material is diamond-like carbon.
 15. The source according toclaim 1, wherein the first material comprises sp³-bound carbon.
 16. Thesource according to claim 15, wherein the first material comprises atleast one additive selected from the group consisting of sp²-boundcarbon, hydrogen, nitrogen, fluorine, and boron.
 17. The sourceaccording to claim 1, wherein the first material consists essentially ofdiamond-like carbon.
 18. The source according to claim 1, wherein thesecond material comprises a metal.
 19. The source according to claim 18,wherein the metal comprises at least one element selected from the groupconsisting of Ti, Pt, Al, W, V, Hf, Fe, Co, and Ni.
 20. The sourceaccording to claim 1, wherein the second material comprises asemi-conductor material.
 21. The source according to claim 20, whereinthe semi-conductor material comprises at least one element selected fromthe group consisting of Si, Ge, In, Ga and As, P, and Sb.
 22. The sourceaccording to one claim 1, further comprising a voltage supply configuredto supply to supply a voltage to each of the first and second electricalterminals.
 23. The source according to claim 1, wherein a surface of thebase includes a convex surface portion extending around an end of thetip close to the base.
 24. The source according to claim 23, wherein aradius of curvature of the convex surface portion of the base is between10 μm and 0.1 μm.
 25. The source according to claim 1, wherein the basehas a surface portion having a surface shape of axial symmetry relativeto an axis of symmetry, and an angle between the axis of symmetry and alongitudinal direction of the tip is less than 10°.
 26. A method,comprising: forming a core of a first material on a base using at leastone deposition process selected from the group consisting of electronbeam induced deposition and ion beam induced deposition; applying acoating of a second material on the core; and arranging the coreopposite to an opening of an extraction electrode, thereby forming anelectron beam source.
 27. A system, comprising: a source according toclaim 1, wherein the system is an electron beam system.
 28. A method,comprising: using a source according to claim 1 to perform at least oneof the following: a) generate an electron beam having an electron beamcurrent of at least 0.1 μA; b) generate an electron microscopic image ofan object; and c) expose a sensitive layer with a predetermined pattern.